GEOL 3045: Planetary Geology

1
GEOL 3045 Planetary Geology

• Lysa Chizmadia
• Edgeworth-Kuiper Belt

2
Introduction

• Discovered in 1992 by David Jewitt Jane Luu
• Estimated gt70,000 objects gt100km
• Estimated mass 0.06-0.3 x ?
• Source for short-period comets
• Period lt 200 years

HST image
Images from http//www.nineplanets.org/kboc.html
Image fromMalhotra Williams (1997)
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Structure of the Kuiper Belt

• EKB from 30-55 AU
• Main body from 32 at 39.5Au to 12 at 48AU
• Thick up to 10? outside ecliptic
• More diffuse distribution extends further

Image from http//en.wikipedia.org/wiki/Kuiper_be
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Kuiper Belt Objects

• NH3, CH4 H2O ices
• Quaoar
• Xline H2O, not amorph
• resurfaced

Images from http//en.wikipedia.org/wiki/Kuiper_b
elt
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Types of KBOs

• Name is controversial
• AKA Trans-Neptunian Objects (TNOs)
• Includes KBOs but also all other objects orbiting
  Sun at the edge of the solar system
• Three main groups
• Classical objects
• Resonant objects
• Scattered objects

Images from http//en.wikipedia.org/wiki/Kuiper_b
elt
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Classical Objects

• AKA cubiwanos (Q-B-1-os)
• 42-47 AU
• No resonances w/ Neptune
• Two populations
• Dynamically cold
• Nearly circular orbits (elt0.1)
• Low inclinations lt10?
• Redder compositions
• Formed in position, may have migrated w/
  Neptune
• Dynamically hot
• Nearly circular orbits (elt0.1)
• Higher inclinations lt30?
• Thought to have formed near Jupiter the ejected

Image from Jewitt Luu (1995)
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Resonant Objects

• Locked in mean motion resonances with Neptune
• 23 Pluto Plutinos
• Semi major axis 39.4 AU
• 200 objects
• 12 called twotinos
• Semi major axis 47.7 AU
• Sparesely populated
• Minor resonances
• 34, 35, 47, 25
• gt50 AU Kuiper Cliff

Image from Jewitt et al. (1998)
Image from http//en.wikipedia.org/wiki/Kuiper_be
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Scattered Objects

• High eccentricities
• 0.59
• High inclinations
• 24
• Origin of Jupiter-family comets

Image from Duncan Levison (1997)
Image from http//en.wikipedia.org/wiki/Kuiper_be
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Pluto System

• Barycenter between Pluto Charon
• At least 3 moons
• Charon (double object)
• Nix (in same plane as Charon)
• Hydra (16 res w/ Charon)
• Atmosphere
• N2, CH4, CO
• Structure (?1.8-2.1 g/cm3)
• 1) Frozen N2
• 2) H2O ice
• 3) Silicate H2O ice

Image from http//en.wikipedia.org/wiki/Pluto_28
astronomy29
Images from http//en.wikipedia.org/wiki/Charon_(
moon)
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Pluto As A Planet

• Pro
• Hydrostatic equilibrium (spherical shape)
• Primarily orbits Sun
• Larger than 1000 km
• Largest object in general vicinity (has cleared
  its neighborhood)

• Con
• High inclination
• High eccentricity
• Orbits barycenter w/ Charon
• Not largest object in KB (has not cleared its
  neighborhood)

Images from http//en.wikipedia.org/wiki/2006_def
inition_of_planet
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Centaur Comets

• Orbit between Jupiter Neptune
• Orbits not stable
• At least 3 display cometary comas
• Probably from KB
• Reflectance spectra
• Amorphous carbon
• Hydrocarbons
• Methanol ice

Image from Stern Campins (1996)
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Formation Theories

• The classical resonant KBOs probably not
  primordial
• Inclinations eccentricities too high
• Three formation theories
• Long-term effects of planetary perturbations
• Resonant sweeping due to planetary migration
• Massive scatterers resulting in impacts
  gravitational perturbations
• As of 2006, 9 other star systems have KB-like
  disks

Images from http//en.wikipedia.org/wiki/Kuiper_b
elt
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Summary
New Horizons

• From 33-50 AU
• Composed of NH3, CH4 H2O ices
• Quaoar has crystalline H2O ice on surface
• Evidence for resurfacing
• Three types of objects
• Classical
• Resonant
• Scattered
• Centaur comets similar compositions
• Probably originated in KB

• Plutos status as a planet
• Hydrostatic equilibrium
• Primarily orbits sun
• Has cleaned up neighborhood?

Image from http//en.wikipedia.org/wiki/Kuiper_be
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